The present invention tackles the problem of controlling gear shifting in cycles and has been developed with particular attention paid to the possible application to competition bicycles. In any case, the reference to this possible application, and in particular the reference to the application to racing bicycles, must not be interpreted as limiting the possible field of application of the invention.
Over the last few years there has developed, in the cycle sector, the tendency to associate to the cycle sensors of various nature so as to be able to acquire information of various kinds regarding the use/behaviour of the means, the aim being to be able to intervene through actuators to modifyxe2x80x94according to certain criteria, and acting both in an automatic way and according to specific commands issued by the user ? the conditions of use/behaviour of the means, in particular as regards its set.
In particular, the present invention has been developed with specific reference to the servo systems which carry out positioning of the transmission chain of the cycle in a position corresponding to the front derailleur and to the rear derailleur.
In drive trains mounted on cycles of a more sophisticated type it is envisaged that the toothing of the crankwheel and sprockets on which the derailleurs act are not all made up of teeth that are the same. Instead, the teeth are arranged in ordered sets and the teeth comprised within each set have a sequence of differentiated geometries such as to facilitate shifting of the chain, the foregoing in order to create, within the corresponding toothing, points or areas in which the movement of shifting of the chain is facilitated. Said points or areas are referred to simply as xe2x80x9cfacilitating portionsxe2x80x9d.
If a command for shifting of the chain position is issued at an inopportune moment, the correct positioning of the chain may be at least momentarily hindered, and hence delayed.
This drawback, which is anyway noticeable in systems for control of gear-shifting of a manual type, becomes particularly troublesome in cycles in which the change of transmission ratio is controlled by an automatically operated actuator, which is governed by an electronic control system. Such a system is usually configured to co-ordinate the various interventions of modification of set of the cycle itself (both according to the commands issued by the user and in an altogether automatic way), so as to optimize the performance of the cycle and, more in general, of the cycle-user system.
As is recognized, for example, in the European patent application EP-A-1 010 612 (on the other hand published after the date of priority of the present application), in the framework of these systems, the attempt to control shifting of the chain at a wrong moment may give rise to various problems.
For example, in addition to an undesired retardation in actuation of the command, a problem may arise linked to the fact that the actuator involved by the command ends up being activated (and hence absorbing energy) for an interval of time in which the actuator itself is not able to ensure that the action requested will be carried out. During this interval, the actuator absorbs power from supply sources (typically batteries) mounted on the cycle, this amounting to energy which, to all effects, ends up being wasted without obtaining any useful result.
The aim of the present invention is to provide a solution that is able to overcome the drawbacks outlined above.
According to the present invention, this purpose is achieved thanks to a process having the characteristics specifically called for in the claims which follow.
The invention also relates to the corresponding system, as well as to components usable in the context of the aforesaid system and/or for implementation of the aforesaid process.
Basically, the solution according to the invention is along the lines of innovation that have led to an increasing sophistication in the control systems usable on cycles, and in particular on competition bicycles, with the aim of acquiring information that may be used for optimizing the supply of energy, avoiding the waste that occurs in systems designed usually to be supplied via batteries, with the evident need to prevent the cycle from being rendered heavy by batteries that are too cumbersome and/or weigh too much.
In a preferred embodiment, the solution according to the invention involves using a transducer that may be positioned in alignment with the crank axle of the cycle. This is preferably a transducer of a potentiometric type, capable of detecting information, such as:
movement of the transmission element of the cycle (whether this is a chain or a belt);
the corresponding direction of movement;
the angular position (or xe2x80x9cphasexe2x80x9d) of the corresponding toothing of the gear wheel driven by the crank axle of the cycle; and
the pedal cadence.
This information may be, at least in part, used to condition activation of members of the cycle moved by means of actuators which draw energy from power-supply sources, such as batteries mounted on the cycle itself.
This applies in particular as regards the operation of the front and/or rear derailleur in order to obtain carrying-out of the shifting operation at the most favourable moment, i.e., when the chain is in a position that exactly corresponds to one of the xe2x80x9cfacilitating portionsxe2x80x9d referred to in the introductory part of the present description.
In this connection, it should be noted that shifting of the chain, or more in general of the element for transmitting motion, may take place properly only if the element itself is moving; otherwise, there is the risk of causing waste of energy and undesirable stresses on the mechanical parts.
A pure and simple signal of movement is not, however, sufficient, given that, if the chain moves in a direction opposite to the desired one (i.e., in the direction opposite to the direction of pedalling to make the cycle advance), again an undesired result is obtained.
Consequently, the solution according to the invention in general involves performance of the operation of gear shifting according to whether it is recognized that the chain itself is moving, and in the desired direction (i.e., in the same direction as that of pedalling to make the cycle advance), as well as to whether the gear wheel involved in gear shifting is in a given angular position (in turn corresponding to the location of the chain in a position that corresponds to one of the aforesaid facilitating portions).